Salt and heat: The effects of elevated temperature at different salinities on seedlings of the red mangrove (Rhizophora mangle L.)

Due to anthropogenic climate change, temperatures are increasing, placing tropical forests, including mangroves, at increased risk of heat stress. The red mangrove (Rhizophora mangle) is a salt-tolerant tree species, with ecological and social importance in the coastal regions of Panama and many other parts of the Americas. It remains unclear how heat stress interacts with seawater salinity in this species. We hypothesize that elevated temperatures reduces overall biomass accumulation and photosynthetic performance, but increases photosystem II heat tolerance through short-term acclimation, whereas increased salinity reduces these traits.

To address this question, an experimental study is currently being conducted in glasshouses exposed to full solar radiation in Panama, where red mangrove seedlings are grown under two temperature settings: ambient temperature and elevated temperature (+5 °C above ambient). Within each glasshouse, eight seedlings are grown per salinity treatment at four salinity concentrations (<0.5 ppt, 5 ppt, 20 ppt, and 35 ppt) in hydroponic systems. This study will provide insight into how the combined effects of salinity and heat influence biomass accumulation and allocation, photosystem II heat tolerance, photosynthetic gas exchange and ionic content of red mangrove seedlings.